Method of producing titanium



June 24, 1958 D. s. cHlsHoLM Erm. 2,840,455f

METHOD 0F PRODUCING TITANIUM Filed ocu 2o. 1952 I5v Sheets-Sheet 1 June24, 1958 D. s. cHlsHoLM :TAL l 2,840,465A

METHOD oF PRoDUcING TITANIUM v l Filed oct. 2o. 1952 f 3 sheets-sheet 2Il: Mg loar/l'c/es i i g I I gfelf Tis/conge O n Il INVENTORS.

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A TTORNE YS June 24, 1958 n. s. cHlsHoLM Erm. 2,840,465

METHOD 0F PRODUCING TITANIUM Filed oct. 2o, 1952 s sheetsheet :s

Aff in J 66 INVENToRs. @Dug/0s CM'S/m/n BY om F. f-/a// Arrow/YsMari-ion on rnonucnso TITANIUM 1 Douglas S. Chisholm and Don F. Hall,Midland, Mich.,V

assignors to The Dow Chemical Company, Midland, Mich., a corporation ofDelaware Application Uctober 20, 1952, Serial No. 315,604 s calms. (ci.lsaaa arent method of and apparatus for the production of the metals,-titanium and zirconium, by reacting a volatile halide thereof,especially the tetrachloride, with magnesium.

Heretofore in the reduction of titanium tetrachloride,

for example, in accordance with the reaction: ZMg-l- TiCl4=Ti-l- 2MgCl2,the magnesium used has been in the form of a pool of themolten metal ina retaining vessel with the upper surface ofthe poolrexposed to thevapor of the titanium tetrachloride. In the `ensuing reaction, there isformed a sponge-like mass of metallic titanium in situ, together withmolten magnesium chloride as a by-product. A number of disadvantagesnure to this practice which limits its usefulness. VAmong thesedisadvantages are that some of the magnesium becomes occlucled in thetitanium sponge yand is thus prevented from being used, thereby loweringthe eiliciency ofthe reduction operation. The sponge so-formed in situsticks to the Walls of and tends to form a bridge in the retainingvessel and is diicult to remove, in spite of the fact that the magnesiummetal during-the reduction more or less floats upon molten magnesiumchloride. Another disadvantage is that the reaction tends to'getfout ofcontrol allowing the magnesium to overheat and vaporize, therebyproducing an undesirable flame-like ret action in which the magnesium`burns as avapor inthe titanium tetrachloride vapor forming dust-likeparticles of metallic titanium instead of sponge. Thedust-like'particles of titanium thus produced are exceedingly .difcult, if notimpossible, to recover as massive titanium metal. Another disadvantageis that the titanium sponge is bulky and very reactive vwhile hotnecessitating essentially batchwise operation to permit cooling for theremoval of the Vsponge from the-retaining vessel and replacement of thesupply of magnesium metal for the reduction. Similar diiiculties arisein the reduction of zirconium tetrachloride with magnesium. insofar aswe are aware, there is neither a method nor an apparatus: extant for theproduction Vof either titanium or zirconium metal by the reduction ofthe tetrachloride of these metals with magnesium which are not hamperedin one way or another by the foregoing diiiiculties. Accordingly, it isthe principal object of the invention to provide an improved method Vofand apparatus'for carrying out the reduction of the aforesaid halidesYWithout the diticulties attendant upon; the use ofthe conventionalmethods and means.- Otherobjects andLadvantages will become apparent asthe `description of the invention proceeds.

Pursuant to the present invention,'it has 'been dis-` covered inreacting titanium tetrachloride v'apor,Y for with apparatus forpracticing the same.

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Patented June 24, 1958 vapor, ignition and smoldering ofthe powder`occurs inv from the zone of formation as the particles fare brought toignition temperature. At the same time by abstracting sufficient of the.resulting heat of the reducing lreaetion'frorn the smolderingmass ofmagnesium'particles through the supporting surface, they are preventedfrom bursting into llame and the reacting particles are maintained in asmoldering do lnot run together, instead they remain `as a porous mass,thereby providing interstices throughout the pile.

The titanium tetrachloride vapor is thereby .enabled to,

permeate the-pile and use all the magnesium particles, and much of themolten magnesium chloride is able.' to more or less drain Vaway from thesmoldering portion of the train as the reaction proceeds. As a result,there is yformed inrsitu a Vtitanium sponge occupying a space abouttwice that ofthe consumed train orl piley of mag-v nesium particleswithout producing titanium metal dust,

the sponge being substantially free from unreactedmagnesium metal.Moreover, the sponge so-'producedimay be readily removed from theIsupporting surface VVbeyond the smoldering zone of the trainwithout'interrupting the reductionv operation. The method is preferablycarried out in continuous manner by continuously lengthen-l ing thetrain or pile 'of magnesium particles at oney end ahead of thesmoldering portion,l at arate sufficientl to keep Va supply of magnesiumparticles aheadof Vthe smoldering ones,-while removing` theproducedsponge from the other end behind the smoldering portion.Analogous results are obtained on applying the same methodY withzirconium tetrachloride vapor. The invention then consists of the.improved methodand apparatus herein fully described and particularlypointed` out in the claims, theannexed drawing and following descriptionsetting forth various modes of practicing the invention. K Y 'j H In thesaid annexed drawing, Fig. 1 is a'sc'hematic diagram illustrating themethod of the invention together.l

Fig. 2 is a side elevation largely paratus according to the invention.

Fig. 3 Ais a horizontal section line 3h3 of Fig. 2.

in section. of, an'. ap-

On referring to Fig. l, it will be apparent that this is ydiagrammaticrepresentation of the method generally`out` lined above and the ligureillustrates the-principle of carrying out the reaction in accordancewith the inven-l particle feeder 4, 'above the supporting surface fordel Y* positing thereupon the. magnesium particles, ,the .rate ofexample with magnesium, that by particulating the magtion, as applied tothe production of titanium, for example,

by a controlled smolden'ng of a trainV orpile of particles of magnesiumin an atmosphere oftitanium'tetrachloride vapor. In this figure isshown, a supporting surface" 1, on which the reaction of the magnesiumparticles with the halide vapor is to take place; The supporting surface`is provided with ltemperature control means comprisingsetv of pipes 2,embeddedy in the supporting' surface,

through Vwhich air at a suitable temperatureimayibe passed. Thesupporting surface is placed within'an enve lope, not shown, forretaining an ambient atmosphere=3 of titanium tetrachloride vapor withwhich the magnesium particles( Aare to react. Means areprovidedsuch'as-'the deposition beingsubject to control, as by means oflt-lle valveS. A Withthis `apparatus, a train of particulated magnesiumis show-n as havingbeen depositedfupon'thesupprtng state until consumed.Theparv ticles ,ofmagnesiurn Vthus treated reach a temperature` t at.least above that of the molten magnesium chloride formed in thereactionas a by-product,.but the particles f' of the apparatus on the:

3 surface by a relative sideways movement of the feeder outlet 6 withrespect to the supporting surface in the direction of left to right. Thetrain of particles Yso-formed passes 4through a number of changesoccurring in sequence' in more or less distinct Zones moving'along thetrain in the ensuing reaction which consumes the train as it formsleaying Vtitanium sponge in situ.

As .to these changes, the train begins, as aforesaid, with thedeposition of the particles on the supporting surface. This. takesplaceu at the pile-.or train-forming zone 7 below the feed-pipe 6 .fromwhich the particles fall. The particles at this stagesare relativelycold; that is the temperature is belowV that at which they willspontaneously ignite in the tetrachloride atmosphere. The pile-formingzone is followedby a preheating zone 8 in which the particles a'resubjected Ato heating bothY by Contact with the-supporting surface andby contact with adjacentparticles already ignited and burning in thefollowing pzone.

The heating which occurs in the preheating zone raises the temperatureof vthe particles progressively alongVv the preheating zone to atemperature atwhich ignition or burning ofthe magnesium particles in thehalide'ratrnosphere begins. Thus, -a-n ignition zone is `establishedadjacent to the hotter end of the preheating zone, as indicated bynumeral 8, the hotter end being remote from the zone of formation. Theignition Zone on the forward end is sharply distinct from the preheatingvzone while the rear of the ignition zone merges into a smoldering zonedesignated by numeral 10 where the particles become hotteras thereaction proceeds. In the front of the smold-V ering zone, the ignitedparticles communicate some of their heat to adjacent unignite-:lparticles and as already mentioned thereby maintain ignition in theignition zone. Burning ofthe particles continues in the smoldering Zoneuntil all magnesium particles are consumed forming titanium sponge insitu as a loaf or cake and molten magnesium chloride.

In the smoldering zone, more than enough heat is liberated -to maintainthe reaction at a smoldering pace, and,accordingly, in this zone, thesmoldering particles are subjected .to a heat exchange in which asucient amount'ofthe heat of the reaction is abstracted from the" pile4as through Athe supporting surface, by means of a cooling air blastthrough pipes 2, to prevent the smoldering particles from overheatingand bursting into flame. The amount of heat exchange required tomaintain the burningof the ignited particles at a smoldering pace isreadily ascertained by trial as by watching Vthe smoldering zone andsuppressing the reaction by cooling the supporting surface enough toprevent flame formation. been found by maintaining the supportingsurface under the smoldering zone at a temperature sufficient to causeignition of the particles in the halide atmosphere but not in excess ofabout 900 to 950 C. the reaction rate can be maintained at a smolderingpace. A preferable temperature for the supporting surface is above thatsuf# cient to maintain the by-product magnesium chloride in the moltenstate (e. g. about 708 C.) but less than about 850 Temperatures lowerthan the melting point of magnesium chloride can be used (e. g. 600 C.)if the solid .magnesium chloride which then tends to collect upon thesupporting surface can be removed.

Bothduring and Ifor some time after the smoldering action,:a substantialproportion of the magnesium chloride drains out of the sponge. The Zoneof Ysuch drainage ofA the trainis indicated at 11 and partially overlapsthe smolderingY zone 10. The resulting partially drained sponge 12ileftat thev end of the smolderingzone, `after all the magnesium hasbeen consumed in reducing tetrachlorideyapor, may be removed from thesupporting surface, asby a cooled scraper 13, in the form of chunks ofsponge 14.

Wby-pro'duct magnesium chloride which in part drains optof the spongeandloff the` supporting. surface L.

It has.

. this'lrnode of operation, theV supporting surface for theA as shown,may be collected in any convenient manner below the supporting surface,and, if desired, reworked for its magnesium content in conventionalmanner for reuse in the method.

The foregoing method may be conducted advantageously upon a movinghearth or supporting sunface which moves sideways away from thetrain-forming zone beneath the magnesium particle feeder at a rate whichis equal, on the average, to the rate at which the zone of ignitionmoves toward the forming end of the train. In this way, the variouszones above described in connection with Fig. l are obtained whichremain in the same relative positions and the process is thereby madecontinuous. In such mode of operation, the path of the train ofmagnesium. particles is preferably madein the form of a segment of acircle as by the use of a revolving supporting surface arranged beneatha magnesium particle feeder which remains stationary with respect to`the supporting surface on which th'eefeeder deposits the particles asthe surface moves. Y l

This mode of operationand `an apparatus therefor is illustrated inFigs?. Vand 3 which will now be described. In

magnesium particles may be in the form of a hollow air cooled disc 15,for example, secured to the lower end ofV thehollow drive shaft 16, thediscV being within the reaction vessel-'17 which holds the atmospherecontaining the titaniumtetrachloride vapor to -be reduced. The reactionvessel 17 is supported in a furnace setting 18'by means ofV which thedisc 15'may be heated to a temperature suicient at least to initiate thereaction of the magnesium with the halide vapor to begreduced andpreferably to maintain the Aby-product magnesium chloride in the moltenstate. The reaction vessel 17 is provided with a gas tight cover 19 forretaining withinV the vessel the atmosphere containing `the halide-vaporwith :which the magnesium is to react. The cover is provided with anopening 20 through which passes the aforesaid shaft 16. The stufng box21, secured to thecover around the'opening 20, provides a gas tight sealfor the shaft 16.V The shaft is supported near its upper end by meansofthe thrust-bearing 22 which rests on supportf23. Drive pulley 24 issecured to the upper end of theshaft and is driven by means of motor 25through the reductionfgearingV `26, pulley 27, and belt 28.

Throughthe hollow shaft 15 Vextends the pipe 29 for.

return air from the hollowdisc escapes up the annular' space 33 betweenthe outside of pipe 29 and the inside of the hollow shaft 16.

The particulated magnesium to be deposited upon the disc 1S isintroduced into the' vessel from a supply hopper 34 through a screwconveyor `35 and feed pipe 36, the outlet 37 of-which is arrangeddirectly over the disc 15 al short distance inward `of its periphery.Receptacle 33 ho'ldsa supply` of the halide .(e. g. liquid titaniumtetrachloride) 'which' is vaporized in the vessel 17 and reduced tometal on the disc' V15.l Thereceptacle 38 is connected to thefinside ofthe reaction vessel through the cover by pipe 39 having a valve 40 forcontrolling the rate of introduction of the'halide into the vessel. A`manometer 41 provides 'a means for ascertaining the difference in thepressure between vthe atmosphere outside the vessel and that on theinside. "Extending through the cover 19 at anoblique angle is aviewingldevice consisting of a tube 42 with a transparent eye-piece 43through which'may be seen the upper sidelof the hollow disc 15. r1he`reaction vessel 17'is provided .Witha hopper bottom 44cmthe `inside'ofwhich. is arranged'theinclined `screw conveyor 45. As shown, the screwconveyor comprises the single plate helixr46 wound on the shaft'47, thehelix having small openings 1S.-'tlzi'enthrcugh tofallowliquidtoldraiuso that the conveyor will not function to elevate liquid. Thelower end of the shaft 47 is journaled in the bearing 49 mounted in thevessel. The upper end of the conveyor extends into an inclined tube 50which passes through the vessel to the outside. Thelower end 51 of theinclined tube extends into the vessel for a sufficient distance to forma seal with the pool 52 of molten magnesium chloride which is maintainedin the vessel during operation. The vessel is provided with an outlet 53below the surface 54 of the pool of molten magnesium chloride, theoutlet being provided with a trap 55 lby means of which the level of thesurface 54 is maintained above the lower end 51 of the inclined pipe.The trap has an outlet 56 outside the furnace setting through whichmolten magnesium chloride is withdrawn from the pool. The upper end ofthe inclined pipe is provided with a ange 57 to which is secured thecover plate 58. The cover plate is provided with an opening 59 whichforms a bearing for the upper end of the screw conveyor shaft 47. Nearthe upper end of the inclined tube 50 is a downwardly extending T, 60,having a flanged opening 61 to which Vmay be detachably secured thevessel 62 by means of clamps 63.

An air cooled scraper indicated generally by numeral 64 (Fig. 3) isprovided over the disc 15 for removing the metal sponge formed thereon.As shown, this device comprises a hollow scraper head 65 carried on oneend of a hollow shaft 66 by means of which the head 65 is moved back andforth across the upper surface of the disc 15 as indicated in dottedoutline. The shaft 66 extends through a tube 67 one end of which isjoined to the side of the vessel 17, around an opening 68 therein, andthe other extends through the side of the furnace setting 18.Y A stungbox 69.is provided on the outer end of the tube 67 for making a sealaround the shaft 66, the seal permitting longitudinal reciprocatorymovement Without leakage of air into the vessel 17. A bearing in theform of an annular ring 70, together with the stuling `box 69,maintainsthe shaft 66 aligned in the bore of tube 67. Reciprocatory motion of theshaft 66 is provided through the link 71 connecting the shaft with thecrank pin 72 on gear wheel 73 which is rotated by pinion 74 on motor 75.

Cooling of the scraper head 65 is elected by means of the pipe 76 whichextends through shaft 66 to near the inside of the working face 77 ofthe scraper head. The pipe 76 is connected by a iiexible hose 78 `toasource of air (not shown). The air delivered by the pipe 76 to thescraper head exhausts through the annular space 79 between the inside ofthe shaft 66 and the outside of the pipe 76.

ln operation, as with titanium tetrachloride for example,

number of more orls distinct zones of action which characterize themethod. 4With the apparatus of Figs; 2 and 3, a series 'of zones similarto that of Fig. 1 is formed butin a train having the form of a segmentof a circle instead of a straight line since the train is deposited upona revolving surface from a fixed feeding point. Referring to Fig. 3 inparticular, these zones are indicated as follows: pile or train-formingzone, 81; Vpreheating zone, 82; ignition zone, 83; smoldering zione, 84;drainage zone, 85; sponge removal zone, 86. The depth of the pile ortrain is controlled by the rate of actuation of the screw conveyor 35 aswell as by the rate of turning of the disc l15.

The depth of the train which gives satisfactory burning or smolderingdoes not appear to be sharply critical. If the train is relatively thinpropagation of the smoldering zone yinto the preheating zone is more orless erratic and discontinuity of operation may result.` .If the traindepth is excessive, there is a tendency for some magnesium particles tobe left unburned. Proper depths for the train are readily ascertained bytrial during operation and are 'evidenced by continuity of the burningorV reaction of the magnesium in the tetrachloride vapor without llame,and

the absence of unconsumed magnesium particles in the resulting sponge.Successful operation' has been had, for

' example, at depths ranging from 1A: inch to as much as 11/2 inches. Y

In any event, the rate of turning of the disc mustnot exceed the rateVat which the ignition zone 82 progresses along the train which becomesheated, then ignites, and Smolders in zones progressing along thetrainas indicated in the drawing. It will be understood that the'lengthsof 'the zones is not critical and varies with operating conditions, andsufficient time should be allowed in generating the train for thesmoldering to be completed before removing the sponge from the disc.` Bydirecting the viewing tube at the point in thetrain where the ignitionzone merges into the preheating zone, the ratev of turning of the disccan be adjusted readily to that which will'maintain the ignition zoneclose to the pileor train-forming the reaction vessel is maintained at atemperature sucient to maintain the pool 52 of magnesium chloride inYthe molten state, the molten magnesium chloride of the pool forming aseal against the escape of tetrachloride vapor from the reaction vesselthrough the outlet 53 and the tube 50. The tetrachloride to be reducedis introduced into the reaction vessel at a rate preferably suti'cientto maintain therein a slightly greater pressure of the halide vapor thanthe atmospheric pressure outside the vessel. In starting up, the heatingof the vessel by the furnace setting 18 in time heats the hollow disc 15until it is hot enough to initiate the reducing reaction betweenparticulated magnesium and the tetrachloride vapor. When the disc isthus made sufficiently hot feeding thereon of the train of particulatedmagnesium is begun. This is accomplished by revolving the disc 15 slowlyby starting motor 25 and operating the screw conveyor 35 so as to conveymagnesium particles from the supply hopper 34 to the upper surface ofthe disc 15. While magnesium particles are allowed to fall from theoutlet 37 ontothe slowly moving disc 15, a train of particles is therebylaid down as indicated at 80. As already explained in connection withFig. l, that by the formation of the train of magnesium particles upon aheated supporting surface in the tetrachloride atmosphere, there isestablished in theV train a tion is continuous, is for example fromabout 0.1 to 0.5

foot per minute for particles passing through a No. V20 sieve with 95percent retention on a No. 200 sieve and laid in a train containingperlineal foot from` lto 36 grams of magnesium. For example,.a disc, 20inches kin diameter on which is formed a pile of magnesium particles Y'in the form of a segment of aY circle about 2 incheswide and about 21/2Vinches. from the periphery of the disc, may be turned at the rate ofabout 0.2 to 0.6 R. P. M. depending upon the rate of smoldering. Thesmoldering zone thus moves along the sequential train on the disc inV adirection opposite to that in which the disc rotates, and, by a suitableregulation of the speed of rotation ofthe disc, is maintained constantlyat about the same position with respect to the outlet 37 duringoperation. Thevbyproduct magnesium chloride in part drains out oftheresulting sponge in the drainage zone 85 and drips off the disc into thepool 52 while the disc turns.

y The partially drained sponge left after the smoldering has ceased isperiodically pushed or scraped ol the 'disc in chunks by the. cooledscraper head 65, which is caused to reciprocate back and forth acrosstheV path of `the train by actuating motor 75, the head being cooledsuliiciently to prevent the sponge from sticking to it` by directing airinto the head through theV hose 78 Withl this scraper device, the`sponge is somewhat compacted on be- Iing subjected to the pressure ofthe scraper head as it pushes against the sponge in scraping it off thedisc, as the sponge is at a temperature generally above 708 C., themelting point of magnesium chloride, and somewhat plastic at this stage.The resulting more or less compacted hot chunks or pieces of sponge fallinto the pool 52 of molten magnesium chloride and on actuating the screwconveyor 4S are carried out of the pool through a seal `of magnesiumchloride in tube 50 into the vessel 62, out `of contact withair. Aftersufficiently cooling the chunks in the vessel, it may be removed fromthe conveyor and emptied. Much of the by-product megnesium chlorideoverflows through the trap 55 and is discharged at 56, the balance ofthe magnesium chloride is contained in the Vvpores of the sponge.

The titanium sponge thus produced is readily worked into massive metalby conventional methods to yield a high quality metal.

In providing the particulated magnesium for use in the method, it isdesirable to eliminate particles which are dust-like from the feed,although a small amount, such as up toV 5 percent by weight, ofdust-like particles can be tolerated. In general, it is desirable to useparticles larger than those passing through a No. 200 sieve (of thestandard screen scale) to avoid loss by dusting. A rela tively shortdrop, such as 6 inches, from the outlet 37 of the feed pipe to thesupporting surface is desirable as the short drop tends to lessendusting and also undesirable bouncing and rolling of the particles onreaching the supporting surface. Large particles arerobjectionable because on melting they coalesce into still larger molten masses whichtend to flow off the reaction supporting surface without forming thesequence of zones described. Particles between these extremes may beused and may be produced in various known ways, such as by grinding,chipping, milling, and atomizing. Particles which are more or lessequiaxed, such as those made by the usual atomizing methods, produce thebest results. Equiaxed particles as large as those passing through a No.l() sieve may be used, although somewhat finer particles are preferable,such as Athose passing through a No. sieve with at least 95 percentretention on a No. ZOO-sieve.

The particles of magnesium as introduced into the tetrachlorideatrnosphere, on being caught upon the supporting surface for reaction,are relatively cold so that reaction does not commence to a significantextent until the particles are actually in the form of a pile or trainupon the supporting surface. This mode of operation overcomes theclogging at the outlet 37 which can occur when the particles vfedthrough it are too hot or too tineV and tend to burn las they fallthrough the .pipe 36. If desired, an inert gas, such as argon or helium,may be fed into the pipe 36 as though a pipe connection 64 to block thetendency for the vapor of vthe volatile halide to enter the pipe 36 fromthe reaction vessel 17. The dilution, if any, which may result from thepresence of the inert gas in the atmosphere in the reaction vessel doesnot significantly alfect the reduction reaction, although provision forventing the inert gas from the reaction vessel may be required as bymeans of a vented condenser, not shown.

The particles of magnesium may be deposited upon the hearth orsupporting surface at as rapid a rate as that at which the zone ofignition advances in the resulting train or elonfated pile. At the sametime, the halide to be reduced is introduced into the reaction vessel ata rate suflicient to maintain therein a pressure of the halide vaporpreferably in excess of the atmospheric pressure outside the vessel. Forexample, the vapor pressure in the reaction vessel of the halide to bereduced may exceed the atmospheric pressure by 1 to 2O inches of water(as in manometer 4l) but other pressures may be used.

While the invention has been exemplied with particular reference to thedeposition of the train .or pile of particulatedf magnesium upon flatsurfaces, it is to beunderstood that other solid supporting surfaces maybe used in .8 similar manner, although notilat, such as cylindrical orconical surfaces. ln s uch instances, the cylinder or cone, for example,is arrange'dto revolve on its 'axis in such a manner that the undersideof a more or less horizontal plain surface willbe tangent to therevolving surface at least at the place Where the particles aredeposited. It will be found also that even though the supporting surfaceis made to slope away from the point of deposition of the particles soas to facilitate drainage of the by-product magnesium chloride, thetendency for the particles to roll oi i.. reduced, if not completelycounteracted, during their reaction with the halide vapor, the reactionproducts of which give adhesion tothe particles for cach other and thesupporting surface when wet with molten magnesium chloride.

Among the advantages of the invention are that the magnesium, inparticulate 'form and arranged in a pile and made to smolder, becomeslcompletely consumed in the atmosphere of the halide to be reduced.There is, therefore, a maximum efciency of use of the magnesium. Themetal obtained from the reduced halide vapor is substantially all in theform of easily recoverable sponge, there being substantially no producedmetal in the form of dustlike particles which are diicult, if notimpossible, to recover. The method is adapted to continuous operationwithout contamination of the metal product by the atmosphere. Thereduction operation is subject to easy accurate control by regulation ofthe input of particulated magnesium metal and removal o'f reaction heat.The magnesium is not fed onto an already reacting body of magnesiuminstead 'the magnesium reacts with the halide vapor without hindrance'from the magnesium supply for the reaction because theV pile or trainof magnesium particles used in the reduction is formed in the reactionzone before the reaction occurs. The reaction is confined to thesurfaces of the particles of magnesium in the pile or train; hence thewalls of the reaction vessel enclosing the halide vapor to be reduced donnot become fouled up with metal reduced from the halide. The reactionor" the magnesium with the halide vapor can be carried out uponhorizontal or sloping surfaces without confining sidewalls because themagnesium is in patriculate form and the particles neither run togethernor off the surfaces.

We claim:

l. The method of producing titanium sponge by reacting magnesium withtitanium tetrachloride which comprises depositing upon a supportingsurface in an atmosphere containing titanium tetrachloride vapor a pileof magnesium in particulate form, said surface having a temperatureabove the melting point of magnesium chloride whereby the magnesiumparticles burn in the titanium tetrachloride vapor forming titaniumsponge in situ and molten magnesium chloride; removing vheat from theburning pile at a rate sullcient to maintain the burning at a smolderingpace; and draining molten magnesium chloride from the pile as itSmolders.

2. The method of producing titanium sponge by reacting magnesium withtitanium tetrachloride which comprises depositing upon a supportingsurface in an atmosphere containing titanium tetrachloride vapor a pileof magnesium in particulate form, said surfaces having a temperatureabove the melting point of magnesium chloride whereby the magnesiumparticles burn in the titanium tetrachloride vapor forming titaniumsponge in situ and molten magnesium chloride; removing heat from theburning pile at a rate suflicient to maintain the burning at asmoldering pace; draining molten magnesium chloride from therpile as itSmolders; and removing the resulting titanium sponge from the.supportingsurface.

3. The method of reacting magnesium with titanium tetrachloride vaporwhich comprises catching a falling stream of particulated magnesium on aheat-absorbing surface moving in a direction sideways of the stream soas to form an elongated shallow pile ,of Vparticulated magnesium on thesaid surface, said falling stream of particulated magnesium having atemperature below that at which the particles spontaneously ignite intitanium tetrachloride vapor while providing the pile with an ambientatmosphere comprising titanium tetrachloride vapor; maintaining the saidheat-absorbing surface at a temperature of at least 708 C., whereby theportion of the pile remote from the point receiving the falling streambecomes heated and smolders on the said surface in the said atmosphereproducing molten titanium sponge in situ and moltenA magnesium chloride,a portion of said molten magnesium chloride dripping oif theheat-absorbing surface as the particles smolder, the smolderingprogressing along the pile toward the point of formation; removing heatfrom the smoldering portion of the pile through the said heatabsorbingsurface at a rate sufficient to prevent the smoldering portion of thepile from bursting into flame, the rate of sideways movement of theheat-absorbing surface being equal to the average rate of progression ofthe smoldering along the pile; and removing from the heatabsorbingsurface the so-formed titaniumr sponge beyond the smoldering portion. j

4. The method of producing titanium sponge by Vreacting magnesium withtitanium tetrachloride which comprises depositing upon a supportingsurface in an atmosphere containing titanium tetrachloride vapor a pileof magnesium in particulate form, said surface having a temperatureabove the melting point of magnesium chloride whereby the magnesiumparticles burn in the titanium tetrachloride vapor forming titaniumsponge in situ and molten magnesium chloride, a portion of said moltenmagnesium chloride dripping off the supporting Vsurface as the magnesiumparticles burn; removing heat from the burning pile at a rate sufficientto maintain the burning at Ia smoldering pace; collecting in a pool themagnesium chloride which drips oif the supporting surface; andwithdrawing the so-produced titanium sponge from the reaction zonethrough the said pool.

5. The method of producing titanium sponge by reacting magnesium withtitanium tetrachloride which comprises forming an atmosphere containingtitanium tetrachloride vapor in a reaction zone; depositing upon aheat-absorbing surface in the said zone above the bottom thereof a pileof magnesium in solid particulate form, said surface having atemperature above the melting point of magnesium chloride, whereby themagnesium particlesburn in the Said atmosphere forming titanium spongein situ and molten magnesium chloride, a portion of said moltenmagnesium chloride dripping off the heat-absorbing surface as themagnesium particles burn; removing heat from the burning pile at a ratesuicient to maintain the burning at a smoldering pace; collecting in apool below the heat-absorbing surface the portion of the magnesiumchloride which drips off the heat-absorbing surface; and scrap- 'l0 Ying the titanium sponge so-formed olf the heat-absorbing surface intothe said pool. p

6.'The method of reacting magnesium with titanium tetrachloride vaporwhich comprises catching a falling stream of particulated magnesium on aheat-absorbing surface moving in a direction sideways of the stream soas to l.

form an elongated shallow pile of particulated magnesium on the saidsurface, said falling stream of particulated magnesium having atemperature below that at which the particles spontaneously ignite intitanium tetrachloride vapor while providing the pile with an ambientatmosphere comprising titanium tetrachloride vapor; maintaining the saidheat-absorbing-surface at a temperatur-enf at least 708 C., whereby theportion of the pile remote from the point receiving the falling streambecomes heated and Smolders onV the said surface in the said atmosphereproducing titanium sponge in situ and molten magnesium chloride, aportion of said molten magnesium chloride dripping off theheat-absorbing surface as the. vparticles smolder, the smolderingprogressing along the pile toward the point of formation; removing heatfrom the smoldering portion of the pile through the said heat-absorbingsurface. at a rate sufficient to prevent the smoldering portion of thepile from bursting into flame, the ratel of sideways movement of theheat-absorbing surface being equal to the average rate Vof progressionof the smoldering along thepile; collecting in a pool below theheat-absorbing surface the magnesium chloride which drips olf theheatabsorbing surface; and removing from the heat-absorbing surface theso-formed titanium sponge beyond the smoldering' portion.

References Citedin the le of this'rpatent UNITED STATES PATENTS1,321,684 Turner ,Nov. 11, 1919 1,373,038 Weber Mar. 29, 1921 1,558,965Clevenger Oct. 27, 1925 2,205,854 Kroll .Tune 25,` 1940 2,564,337 MaddexAug.14, 1951 2,567,838 Blue Sept. 11, 1951 2,586,134 Winter Feb. 19,1952 2,607,674 Winter Aug. 19, 1952 2,663,634 Stoddard Vet al Dec. 22,1953 2,763,542 Winter Sept. 18, 1956 2,766,113 Chisholm et al Oct. 9,1956 FOREIGN PATENTS l 386,621 Great Britain Feb. 16, 1933 832,205Germany Feb; 21, 1952 686,845 Great Britain Feb. 4, 1953 OTHERREFERENCES Metal Powder Report, vol. 7, No. 4, December 1952, page 50. Y

1. THE METHOD OF PRODUCING TITANIUM SPONGE BY REACTING MAGNESIUM WITHTITANIUM TETRACHLORIDE WHICH COMPRISES DEPOSITING UPON A SUPPORTINGSURFACE IN AN ATMOSPHERE CONTAINING TITANIUM TETRACHLORIDE VAPOR A PILEOF MAGNESIUM IN PARTICULATE FORM, SAID SURFACE HAVING A TEMPERATUREABOVE THE MELTING POINT OF MAGNESIUM CHLORIDE WHEREBY THE MAGNESIUMPARTICLES BURN IN THE TITANIUM TETRACHLORIDE VAPOR FORMING TITANIUMSPONGE IN SITU AND MOLTEN MAGNESIUM CHLORIDE; REMOVING HEAT FROM THEBURN-